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Registered Member #1811
Joined: Sat Nov 15 2008, 11:52AM
Location:
Posts: 14
Im planning to make a single element wire like a loop that wraps round a glass bottle, heats up to red hot, then with a drop of water the bottle is cut finely into a ring for mosaic tables. I have done this thing smallscale for glass tubing for my laboratory but this is bigger. The element wire im using is 1-1.5 mm and is 50 cm long and has 1 Ohm of resistance. Its going to be preferably powered from the mains or a welding machine (90-110VAC or DC). on a mains I=V/R means il have 240A or 90A unless i use a current adjustable welding machine which is my last option. How else can i limit current to this element? I powered at 240v through 3 1.2k ceramic resistors in parallel limited for 5w each making 500 ohms at 15w and they got hot at 90w. This was a test but it shows il need at least 300 watts for making this red hot. Would 3 big transistors be an option to make it adjustable? Thanks for all the info guys this is for my mom :P
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Cypriotica wrote ...
The element wire im using is 1-1.5 mm and is 50 cm long and has 1 Ohm of resistance. I... need at least 300 watts for making this red
So you want on the order of 17 volts at 17 amps. With junk in -my- garage, I would choose a Variac feeding a rewound MOT or other low-V, high-I power transformer.
If you can shorten your heater wire enough to cut bottles with 12 to 14 volts, you can use a 12-volt lighting transformer or perhaps a car battery charger (or, of course, a car battery).
In my experience cutting glass bottles with hot wires, the critical power level does -not- coincide with red-hot-in-open-air. One successful method included filling bottle with cold water just up to the level of scribed cut line.
Good luck. Rich p.s. Here's an industrial application of hot wire to cut open color CRT's: at 2:45 in
Registered Member #1811
Joined: Sat Nov 15 2008, 11:52AM
Location:
Posts: 14
Im going to try the car battery first, but the rewound MOT would be handy. I have 2 MOT's just lying around in my room so that would work. How many turns on the secondary for 17 volts and how would i feed it with a variac? I havent used variacs before... I watched the video, nice job the guys are doing. Also i have a 8 ohm resistor from a large angle grinder. This is rated for 2000w and is wire and ceramic. I could hook this up to a 300 amp adjustable arc welding machine. Problem solved i guess!! What wattage do you think this element would melt at? Thanks for the reply Klugesmith.
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Some questions in an element designed to cut glass bottles into rings for crafts use
